A decision by International Hydrographic Organization in spring of 2000 delimited a fifth world ocean - Southern Ocean - from southern portions of Atlantic Ocean, Indian Ocean, and Pacific Ocean. Southern Ocean extends from coast of Antarctica north to 60 degrees south latitude, which coincides with Antarctic Treaty Limit. Southern Ocean is now fourth largest of world's five oceans (after Pacific Ocean, Atlantic Ocean, and Indian Ocean, but larger than Arctic Ocean).

Geography

Southern Ocean

Location:

body of water between 60 degrees south latitude and Antarctica

Geographic coordinates:

65 00 S, 0 00 E (nominally), but Southern Ocean has unique distinction of being a large circumpolar body of water totally encircling continent of Antarctica; this ring of water lies between 60 degrees south latitude and coast of Antarctica and encompasses 360 degrees of longitude

Map references:

Antarctic Region

Area:

total: 20.327 million sq km
note: includes Amundsen Sea, Bellingshausen Sea, part of Drake Passage, Ross Sea, a limited part of Scotia Sea, Weddell Sea, and other tributary water bodies

Area - comparative:

slightly more than twice size of US

Coastline:

17,968 km

Climate:

sea temperatures vary from about 10 degrees Celsius to -2 degrees Celsius; cyclonic storms travel eastward around continent and frequently are intense because of temperature contrast between ice and open ocean; ocean area from about latitude 40 south to Antarctic Circle has strongest average winds found anywhere on Earth; in winter ocean freezes outward to 65 degrees south latitude in Pacific sector and 55 degrees south latitude in Atlantic sector, lowering surface temperatures well below 0 degrees Celsius; at some coastal points intense persistent drainage winds from interior keep shoreline ice-free throughout winter

Terrain:

Southern Ocean is deep, 4,000 to 5,000 meters over most of its extent with only limited areas of shallow water; Antarctic continental shelf is generally narrow and unusually deep, its edge lying at depths of 400 to 800 meters (the globel mean is 133 meters); Antarctic icepack grows from an average minimum of 2.6 million square kilometers in March to about 18.8 million square kilometers in September, better than a sixfold increase in area; Antarctic Circumpolar Current (21,000 km in length) moves perpetually eastward; it is world's largest ocean current, transporting 130 million cubic meters of water per second - 100 times flow of all world's rivers

huge icebergs with drafts up to several hundred meters; smaller bergs and iceberg fragments; sea ice (generally 0.5 to 1 meter thick) with occasionally dynamic short-term variations and with large annual and interannual variations; deep continental shelf floored by glacial deposits varying widely over short distances; high winds and large waves much of year; ship icing, especially May-October; most of region is remote from sources of search and rescue

Environment - current issues:

increased solar ultraviolet radiation resulting from Antarctic ozone hole in recent years, reducing marine primary productivity (phytoplankton) by as much as 15% and damaging DNA of some fish; illegal, unreported, and unregulated fishing in recent years, especially landing of an estimated five to six times more Patagonian toothfish than regulated fishery, which is likely to affect sustainability of stock; large amount of incidental mortality of seabirds resulting from long-line fishing for toothfish
note: now-protected fur seal population is making a strong comeback after severe overexploitation in 18th and 19th centuries

Environment - international agreements:

Southern Ocean is subject to all international agreements regarding world's oceans; in addition, it is subject to these agreements specific to Antarctic region: International Whaling Commission (prohibits commercial whaling south of 40 degrees south [south of 60 degrees south between 50 degrees and 130 degrees west]); Convention on Conservation of Antarctic Seals (limits sealing); Convention on Conservation of Antarctic Marine Living Resources (regulates fishing)
note: many nations (including US) prohibit mineral resource exploration and exploitation south of fluctuating Polar Front (Antarctic Convergence) which is in middle of Antarctic Circumpolar Current and serves as dividing line between very cold polar surface waters to south and warmer waters to north

Geography - note:

major chokepoint is Drake Passage between South America and Antarctica; Polar Front (Antarctic Convergence) is best natural definition of northern extent of Southern Ocean; it is a distinct region at middle of Antarctic Circumpolar Current that separates very cold polar surface waters to south from warmer waters to north; Front and Current extend entirely around Antarctica, reaching south of 60 degrees south near New Zealand and near 48 degrees south in far South Atlantic coinciding with path of maximum westerly winds

Economy

Southern Ocean

Economy - overview:

Fisheries in 2000-01 (1 July to 30 June) landed 112,934 metric tons, of which 87% previously krill and 11% Patagonian toothfish. International agreements were adopted in late 1999 to reduce illegal, unreported, and unregulated fishing, which in 2000-01 season landed, by one estimate, 8,376 metric tons of Patagonian and antarctic toothfish. In 2000-01 antarctic summer 12,248 tourists, most of them seaborne, visited Southern Ocean and Antarctica, compared to 14,762 previous year.

Transportation

Southern Ocean

Ports and harbors:

McMurdo, Palmer, and offshore anchorages in Antarctica
note: few ports or harbors exist on southern side of Southern Ocean; ice conditions limit use of most of them to short periods in midsummer; even then some cannot be entered without icebreaker escort; most antarctic ports are operated by government research stations and, except in an emergency, are not open to commercial or private vessels; vessels in any port south of 60 degrees south are subject to inspection by Antarctic Treaty observers (see Article 7)

Transportation - note:

Drake Passage offers alternative to transit through Panama Canal

Transnational Issues

Southern Ocean

Disputes - international:

Antarctic Treaty defers claims (see Antarctica entry), but Argentina, Australia, Chile, France, NZ, Norway, and UK assert claims (some overlapping), includes continental shelf in Southern Ocean; several states have expressed an interest in extending those continental shelf claims under United Nations Convention on Law of Sea (LOS) to include undersea ridges; US and most other states do not recognize land or maritime claims of other states and have made no claims themselves (the US and Russia have reserved right to do so); no formal claims have been made in sector between 90 degrees west and 150 degrees west